1. Field of the Invention
The present invention relates to geometric surfaces for mass and heat transfer devices and their method or use. More particularly, it relates to hexahedral, annular and cylindrical fluid distribution surfaces with apertures formed therein for fluid management in a liquid system in at least a partially flooded state. The distribution surfaces are useful for heat and mass transfer in devices such as absorption refrigeration machines.
2. Background
Absorption refrigeration machines are heat operated refrigeration machines that operate on one of the earliest know principles of refrigeration. In their basic form, they consist of an interconnected absorber, desorber (generator), condenser, and evaporator that use a refrigerant and an absorbent as a refrigerant or solution pair and a heat source to transfer heat between a heat load and a heat sink.
The absorber contacts low pressure refrigerant vapor with a miscible absorbent. Absorption takes place as a result of the mixing tendency of the miscible materials as well as an affinity between the refrigerant vapor and the absorbent and results in the generation of thermal energy which is released to the heat sink. The mixture formed by the absorption process, which is referred to here as a strong solution, is typically pressurized by means of a solution pump and conveyed via a heat exchanger to the desorber (generator).
The desorber causes the refrigerant vapor and absorbent to separate as a result of the application of heat. When the absorbent is a nonvolatile material, heating of the strong solution is sufficient to accomplish complete separation of the refrigerant vapor. The remaining absorbent, referred to as a weak solution, is returned to the absorber to again begin the absorption process. When the absorbent is a volatile material such as water in an ammonia/water refrigerant pair, it is desirable to remove a good portion of the volatile absorbent (water) from the refrigerant vapor (ammonia) using an analyzer, which gives a relatively pure absorbent, or a rectifier, which gives a relatively pure vapor, or both.
After removal of absorbent from the vapor if needed, the vapor passes to the condenser. The condenser condenses the refrigerant vapor to a liquid with the liberation of heat. The hot liquid refrigerant then passes to the evaporator. The evaporator revaporizes the hot refrigerant liquid at low pressure and temperature with input of heat from the heat load, i.e., from the refrigerator, room, building, or other medium the system was designed to cool. From the evaporator, the refrigerant vapor enters the absorber to again cycle through the process.
In each of these components, at least two phases are present with mass transfer between the two phases and each typically involves a heat transfer component. The desorber uses heat to separate a strong solution into a vapor and a liquid absorbent (weak solution), the absorber combines the weak solution and vapor with release of heat, the condenser transforms refrigerant vapor to liquid with the release of heat and the evaporator transforms liquid refrigerant to vapor with the application of heat.
In the prior art, metal pipe or tubing, often wound in coils has been the preferred way to transfer heat to or form the mass transfer process. In evaporation or desorption processes, the liquid was flowed or sprayed over a coil of tubing containing a hot liquid to effect evaporation or desorption. Alternatively the heated coil was submerged in a liquid pool. For an absorber or condenser, the vapor was exposed to a coolant coil to achieve condensation while in an absorber, the absorbent was sprayed or dripped over the coolant coil in the presence of vapor. Alternatively the cooling coil was submerged in a pool of the solution.
As shown in U.S. Pat. Nos. 5,617,737 and 5,572,884, tubing can be manufactured with enhanced heat transfer surfaces. However, such tubing is quite expensive, large amounts are needed, and the convoluted shapes are difficult and expensive to manufacture. Moreover they typically require a large amount of space to effect the desired process.
As seen in U.S. Pat. Nos. 5,636,627 and 5,704,417, some effort has been made to use a falling film technique in which a thin film of liquid flows downward and covers the surfaces of the device to effect both heat and mass transfer. Such devices, while not as costly as tubing and pipe, require careful and exact dimensions, tolerances, alignment, configuration and leveling in order to achieve the desired surface wetting. When only a part of the heat transfer surface is wetted, the heat transfer effect is decreased significantly because of the loss of heat transfer area. In high-heat devices such as desorbers, lack of complete wetting can result in burnout, devise warping, and metal fatigue which in turn further accentuate the wetting problem. In addition, fluid and vapor flows must be precisely controlled to avoid flooding and resulting destruction of the falling film and its effectiveness.
Accordingly, it is an object of the present invention to provide a device that maximizes the heat transfer between two fluids.
It is an object of the present invention to provide a device that maximizes mass transfer between two fluids.
It is an object of the present invention to provide a device that is simple and inexpensive to manufacture.
It is an object of the present invention to provide a device that is compact in size.
It is an object of the present invention to provide a device that eliminates warping and component distortion under high heat conditions.
Another object of this invention is to provide a device that affords improved liquid-vapor equilibrium conditions.
Another object of this invention is to provide a device that improves the heat transfer efficiency to or from a heat transfer fluid.
Yet another object of this invention is to provide a heat and mass transfer device that can be used with a wide variety of heat transfer fluids.
Another object of this invention is to provide a device for the effective direct heat transfer between endothermic and exothermic processes.
Another object of this invention is to provide for improved devices that can be more effectively connected to each other.
Another object of this invention is to provide an improved device for use with evaporation, desorption, absorption, condensation, analyzer and rectification processes.
Still another object of this invention is to provide improved components for use in heat transfer absorption machines.
Other objects of the invention will become more apparent to those with ordinary skill in the art from consideration of the present disclosure.